Why only one freight rate is applied to different cargo grades in freight invoice?

Scenario: User has created a one cargo contract which includes different cargo grades with different pricing (freight rates), which belongs to the same counterparty. In addition, all the cargo grades are being loaded and discharged in the same ports. In cargo contract, under Pricing tab, different prices are entered per each cargo grade. Upon raising a freight invoice, one can see three BL quantities of each cargo grades, however they all display the same freight rate rather than various ones.

Cargo contract > Itinerary and Pricing rules:

Freight invoice with wrong freight rates for second and third cargo grades:

Solution: For having different freight rates, it would be recommended to create separate cargo contracts, so that the correct freight rate is picked up for each cargo grade.

If cargo grades with different pricing had a different discharge port, the system would recognize a distinct freight rate without a need of separate cargo contract.

Two cargo contracts with different pricing:

Freight invoice with correct freight rates: